In order to explore those areas which may be dangerous for human (for example, different planets, underground tunnels or caves), exploration robots are used. Exploration robots comprise various sensors for detecting objects in the area they are sent and for identifying the characteristics of the said objects. One of the sensors used in the said exploration robots is tactile sensors. By means of the tactile sensors, presence of certain objects, the force applied by them and some physical features thereof such as pressure and rigidity can be detected.
The conventional tactile sensors comprise a light source positioned under an elastic surface and a light sensing element for sensing the amount of the light reflected from the said surface, as disclosed in US2010155579A1. In such tactile sensors, when a force is applied on the elastic surface, the said surface approaches to the light source and the light sensing element. As a result of such approach, the amount of light incident on the light sensing element increases. The amount of light sensed by the light sensing element and resilience properties of the surface are used to calculate the amount of force applied to the surface. However, in this embodiment, the number of light sources that may be positioned under the unit surface and of the light sensing elements are limited, and it is cumbersome to process data received from a high number of light sensing elements.
Said problems are solved by a module disclosed in WO2014011126A1. The said module comprises an elastic material, which is covered with a layer providing light reflection; a CMOS or CCD image sensor; at least one light source; a plurality of first fiber optic cables, a tips of which are separated from surrounding environment via said layer by being located under the layer and other tips of which are in connection with said light source, wherein said first fiber optic cables carry light beams from the light source to said layer; a plurality of second fiber optic cables, a tips of which are separated from surrounding environment via said layer by being located under the layer and being directed towards the layer and other tips of which are in connection with said image sensor so that each second fiber optic cable is paired with one pixel of the image sensor, wherein light beams reflected from the layer are transferred to the image sensor by said second fiber optic cables; a processor which calculates every individual force applied to the layer according to light intensity changes of each pixel connected with a second fiber cable, of a photo frame generated by the image sensor in response to the displacement of the layer by using image processing techniques. In the module disclosed in WO2014011126A1, when the elastic material contacts to an object, a deformation is generated in the elastic material and the said layer (e.g. displacement of the layer towards the fiber optic cables). As a result of such displacement, the amount of light reflected from the layer to the fiber optic cable is changed. Said change in the amount of light is detected as a color change in the photo frame generated in the image sensor. The processor applies image processing techniques to the said photo frame so as to measure color changes of the photo, and thus the amount of displacement of the layer. Based on the amount of displacement calculated, the force applied on the elastic material is also calculated. By means of the displacement area represented by the area of color change in the image, the pressure applied is calculated. Although the tactile sensation is detected with a high resolution by means of the module disclosed in WO2014011126A1, since the said module can only sense touch, it cannot provide other sensing functions required by an exploration robot.